The present invention relates to an apparatus and a method for the plating and deplating of gallium onto electrically conductive surfaces. More particularly, the present invention relates to a brush plating apparatus for applying gallium to a metal surface.
It is important to distinguish at the outset the fact that the apparatus of the present invention performs an actual plating of gallium onto the desired conductive surface and not just a mere gallium deposition. While commercial solutions for gallium deposition appear to be available, deposition produces only physical contact while plating, on the other hand, results in chemical bonding.
Plating with gallium becomes particularly difficult in those situations in which it is desired to plate only portions of a large workpiece. Because immersion plating of gallium onto metal surfaces requires the use of a relatively strong caustic solution, conventional masking methods are generally unsatisfactory in their attempts to prevent local plating and to protect the surface of the metal from the caustic solution. Even if only partial immersion is attempted, caustic fumes which evolve during the plating process often produce deleterious effects upon the surface of the metal being plated. Furthermore, even in those situations in which successful local gallium plating of a large workpiece is performed, subsequent wear and abrasion may cause localized deplating to occur. In such cases, plating repairs are presently possible only through the methods originally employed to produce the plating, namely, immersion. As above, immersion of only those portions of the workpiece to receive new plating exposes the rest of the plated workpiece to caustic fumes which cause deplating elsewhere or deleteriously affects the surfaces which have not been plated, even stainless steel surfaces. These problems often occur in the situation in which it is desirable to plate only the circumference or edge portions of a large circular workpiece. Additionally, at present there is no satisfactory method to selectively deplate portions of the workpiece which have received excess or uneven plating.